Because the substantive truth of the theology isn’t dispositive of whether family members have a right (in the social, not legal, sense) to criticize each other from departing from certain norms and practices.
For example, there is a lot of evidence showing that the supposed harms of moderate drinking during pregnancy are overstated, and the benefits of breast feeding are overstated. The effect of screen time on kids is also overstated. Just because someone might conclude that advice is wrong, does that mean family members are out of bounds for giving that advice? Or that people shouldn’t have to graciously accept it? There are boundaries, sure, but family members are entitled to express their views on how each other live their lives.
Beyond that, there are objective benefits to religion apart from the truth or falsity of the theological doctrine. Studies show that actively religious people tend to be significantly happier and more socially involved: https://www.pewresearch.org/fact-tank/2019/01/31/are-religio.... Is that a sufficient basis for family members to encourage each other to raise their kids within the community religion, irrespective of the truth of the theology?
Also, there are non-falsifiable moral judgments that are independent of but associated with religion. Secular US culture emphasizes individualism, self expression, and personal fulfillment. Many believe that kids should be raised with a strong sense of duty to family, and the expectation that their purpose in life is to work hard and raise families of their own. These ideas are independent of theological truth. Many non-religious people believe these things too. But if you think it’s important for kids to be consistently exposed to those ideas, you’ll find that most of the people who have those beliefs just happen to be either religious (or Asian, or both). Is it out of line for communities to encourage their members to conform to values that they believe are more conducive to a better world? Whether the underlying theology is true or false doesn’t change the answer.